This invention relates to a stator coil including serially-connected conductor segments (which may be referred to as a serial-joint segmental stator core, hereinafter) for an electric rotary machine and also relates to its manufacturing method.
A conventionally proposed stator coil consists of numerous conductor segments which are inserted into slots of a stator core and serially connected to each other. For example, Japanese Patent No. 3118837 discloses a method of manufacturing this type of coil which includes U-shaped conductor segments being serially connected.
According to this kind of serial-joint segmental stator coil, a pair of legs of a conductor segment is separately inserted into different slots spaced by an angle equivalent to a pole pitch. A protruding part of each leg is bent in the circumferential direction. Then, the distal ends of the legs of different conductor segments are successively joined.
More specifically, the conductor segment consists of a U-shaped (more accurately, a V-shaped) head conductor portion (also referred to as a curved or turning portions), a pair of in-slot conductor portions extending from both ends of the head conductor portion and inserted into different slots from one axial side of a core, and a pair of tail conductor portions protruding out of the slots from the other axial side of the core and extending in the circumferential directions. The distal ends of the tail conductor portions of different conductor segments are joined together. In this specification, the in-slot conductor portion and the tail conductor portion may be collectively referred to as a leg of the conductor segment. Accordingly, the head conductor portions of respective conductor segments cooperatively constitute a head side coil end. The tail conductor portions of respective conductor segments cooperatively constitute a tail side coil end.
Furthermore, Japanese Patent No. 3118837 discloses a small-turning conductor segment and a large-turning conductor segment surrounding the small-turning conductor segment so as to cooperatively constitute a conductor segment set. A total of four legs of the conductor segment set are separately held by two rings coaxially disposed. A pair of legs of each conductor segment is expanded in the circumferential direction by causing a relative rotation between two rings to form head slanting portions.
Furthermore, Japanese Patent Application Laid-open No. 2000-139049 discloses a stator core with numerous slots into which small-turning conductor segments and large-turning conductor segments surrounding the small-turning conductor segments are inserted so as to cooperatively constitute conductor segment sets. A total of four legs of the conductor segment set are separately held by four rings coaxially disposed. A pair of legs of each conductor segment is expanded in the circumferential direction by causing a relative rotation between these rings to form head slanting portions.
Moreover, Japanese Patent No. 3104700 discloses a process of welding a pair of distal end portions of adjacent conductor segments disposed in the radial direction, and also discloses providing an intervening member between two distal end portions of adjacent conductor segments disposed in the circumferential direction.
Japanese Patent Application Laid-open No. 2000-166148 discloses a tail side coil end including a large-turning conductor segment and a small-turning conductor segment having recessed portions which are formed in the vicinity of tail joint portions and respectively extend along opposed sides of their tail slanting portions. According to this arrangement, two tail slanting portions are disposed next to each other in the radial direction and the radial width of each slanting portion is thin in the crossing portion of these tail slanting portions (refer to FIG. 13).
Hereinafter, a conventional method for manufacturing this kind of serial-joint segmental stator coil disclosed in the above-described prior art documents will be explained.
First, a required number of pine-needle shaped conductor segments are prepared. Next, each pine-needle shaped conductor segment is configured into a U-shaped conductor segment with a pair of in-slot conductor portions angularly spaced by one pole pitch in the circumferential direction. Then, the U-shaped conductor segments are spatially disposed (more specifically, aligned in the circumferential direction) so that a required number of conductor segments are simultaneously inserted into the slots of the stator core. For the above-described process, it is possible to use a pair of coaxial rings having insertion holes, for example, disclosed in FIG. 3 of Japanese Patent No. 3118837. According to the manufacturing process shown in this prior art, both legs of a pine-needle shaped conductor segment are separately inserted into two holes of the coaxial rings which are in the same angular position. Then, the coaxial rings are mutually rotated about their axes by the amount corresponding to one pole pitch in the circumferential direction. As a result, each pine-needle shaped conductor segment is configured into a U-shaped conductor segment with a head portion straddling so as to form, as a whole, a U shape (or V shaped) in the circumferential direction.
Next, a process of inserting respective conductor segments, formed into a U-shaped configuration and aligned in the circumferential direction, into corresponding slots of the core is performed. This process is performed by pulling the legs out of the rings having insertion holes, while holding the head conductor portions of respective conductor segments each being formed into a U-shaped configuration and aligned in the circumferential direction, and then inserting the legs of respective conductor segments into slots of the core.
Next, a process for bending each tail conductor portion protruding out of the slot in the circumferential direction is performed. Preferably, each tail conductor portion is bent in the circumferential direction by a half pole pitch. Such circumferential bending process is performed by using a plurality of coaxial rings having insertion holes, for example, disclosed in FIGS. 4 and 5 of Japanese Patent No. 3196738. The distal ends of respective tail conductor portions are inserted into insertion holes of the coaxial rings. Then, each coaxial ring is rotated in the circumferential direction by a half pole pitch (electric angle of xcfx80/2), so that each tail conductor portion is bent in the circumferential direction by a half pole pitch. When each coaxial ring is rotated in the circumferential direction, it is preferable to urge the coaxial ring in the axial direction so as to advance toward the tail conductor portion. The radius of curvature at the bend point can be enlarged. Next, the process of welding the distal end portions of the tail conductor portions is performed according to the predetermined order.
Through the above-described processes, an endless phase coil, as a coil representing one of the phases, is formed. To form leader terminals of each phase coil at the head side, one of the U-shaped head conductor portions of the U-shaped conductor segments is cut at an appropriate position. When the leader terminals are formed long enough, the leader portions can be bent in the circumferential direction so as to provide a connecting wire for a neutral point. The reason why such leader terminals are formed at the head side coil end is to avoid the interference with the welding operation performed at the tail side coil end.
The above-described conventional serial-joint segmental stator coils are preferably used for automotive alternators.
However, the above-described serial-joint segmental stator coils have the following problems.
More specifically, according to the tail slanting portions with the recessed portions as disclosed in the above-described Japanese Patent Application Laid-open No. 2000-166148 (refer to FIG. 13), the press shaping is used to reduce the radial thickness at the recessed portions.
To suppress the increase in the coil resistance caused by the reduction of the cross-sectional area of the conductor when subjected to the press shaping, and also to prevent the interference between the tail slanting portions disposed adjacently in the circumferential direction due to increase of the circumferential width of the conductor, the tail slanting portions are significantly chamfered at the portions where the recessed portions are not formed. The recessed portions subjected to the press shaping have the non-chamfered cross-sectional shape.
However, increasing the sectional rectangle rate (i.e., the reciprocal of chamfering rate) to compensate the reduction in the cross-sectional area of the tail slanting portion at the above-described recessed portion will require the original sectional rectangle rate being set at a small value and also require the sectional rectangle rate obtained after finishing the press shaping to be increased to the level having no chamfering. As a result, an excessively large stress will act on the insulation film covering the conductor segment.
Furthermore, the sectional rectangle rate (=actual cross section/rectangular cross section having the same width and height) of the in-slot conductor portion decreases and accordingly the slot space factor of the slot is worsened. Furthermore, when the original conductor segment has a high sectional rectangle rate, this is unfeasible.
Especially, performing the press shaping for reducing the radial thickness of the tail slanting portion from one side so as to change the sectional rectangle rate will require clamping each tail slanting portion in the circumferential direction to prevent the tail slanting portion from stretching in the circumferential or radial direction. However, clamping the tail slanting portion will damage the insulation film covering the conductor segment.
In view of the foregoing problems of the prior arts, an object of the present invention is to prevent the insulation film from being subjected to a large stress and assure reliable electric insulation between the tail conductor portions.
In order to accomplish the above and other related objects, the present invention provides a stator coil including sequentially-connected conductor segments for an electric rotary machine, including a plurality of conductor segments accommodated in a slot of a stator core having an even number of conductor accommodation positions serially aligned in the radial direction. The conductor segments are sequentially connected to cooperatively constitute one turn of a phase coil of an M-phase (M is an integer not smaller than 3) armature coil. Each of the conductor segments has a pair of in-slot conductor portions separately accommodated into the conductor accommodation positions of two different slots mutually spaced by a predetermined pitch, a head conductor portion continuously extending from the in-slot conductor portions and protruding from one end of the stator core so as to constitute a head side coil end, and a pair of tail conductor portions continuously extending from the in-slot conductor portions and protruding from the other end of the stator so as to constitute a tail side coil end. The head conductor portion has a U-shaped head top portion, and a pair of head slanting portions extending obliquely in both circumferential and axial directions from the head top portion and respectively connected to the in-slot conductor portions. The tail conductor portions has a pair of tail slanting portions extending obliquely in both circumferential and axial directions from the pair of in-slot conductor portions, and tail joint portions formed at distal ends of the tail slanting portions and bonded to tail conductor portions of other conductor segment. The head side coil end includes a plurality of head conductor portions serially disposed in the radial direction when seen from the circumferential direction. And, the tail side coil end includes a plurality of tail conductor portions serially disposed in the radial direction when seen from the circumferential direction. Furthermore, as characteristic features of the stator coil according to the present invention, the conductor segments include a small-turning conductor segment inserted into a pair of conductor accommodation positions disposed next to each other in the radial direction, and a large-turning conductor segment inserted into another pair of conductor accommodation positions respectively disposed next to the above pair of conductor accommodation positions in the radial direction. The tail joint portion of the large-turning conductor segment is bonded to the tail joint portion of the small-turning conductor segment located adjacently in the radial direction. The tail slanting portion of the large-turning conductor segment or the small-turning conductor segment has a swerved portion which bends toward a direction departing from the opposed conductor segment so as to expand a radial clearance between the large-turning conductor segment and the small-turning conductor segment at a crossing portion of the tail slanting portion of the large-turning conductor segment and the tail slanting portion of the small-turning conductor segment which are adjacently disposed in the radial direction.
Namely, according to the present invention, the large-turning or small-turning conductor segment has the swerved portion formed in the vicinity of the tail joint portion so as to bend in the radial direction, instead of forming the recessed portion at one side of the tail slanting portion based on the increase in the above-described sectional rectangle rate. Formation of the recessed portion according to the present invention is not inferior to that of the above-described conventional art in that a sufficient cross section of the conductor segment can be secured. Even when the insulation film covering the tail slanting portion of the large-turning conductor segment is softened or fused when the paired tail joint portions are welded, the insulating film does not contact with the insulating film covering the tail slanting portion of the neighboring small-turning conductor segment which is in a cross relationship with the tail slanting portion of the above large-turning conductor segment. As a result, it becomes possible to adequately maintain the electric insulation between two tail slanting portions crossing with each other.
Furthermore, formation of the recessed portion according to the present invention does not require a complicated technique adopted in the above-described conventional method for increasing the sectional rectangle rate for deforming the tail slanting portion in the radial direction while clamping it in the circumferential direction. Furthermore, no strong stress acts on the insulation film at the sectionally edged portion of the tail slanting portion. Substantially no damage will be caused in the insulation film. The electric insulation can be maintained appropriately. The present invention can be preferably applied to high-voltage motor, such as a vehicle drive motor.
According to the stator coil of the present invention, it is preferable that a plurality of conductor segment sets, each consisting of the large-turning conductor segment and the small-turning conductor segment, are disposed in the radial direction. And, a gap between a pair of conductor segment sets disposed next to each other in the radial direction and a gap between a pair of small-turning conductor segments disposed next to each other in the radial direction are widened in the vicinity of the tail joint portions compared with the gaps in the vicinity of an end surface of the stator core.
According to the stator coil of the present invention, the swerved portion is formed by bending the tail slanting portion toward the radially opposite side. As a result, to prevent the curved portions of the conductor segments from contacting with each other, it is necessary to secure a sufficient radial clearance between neighboring conductor segment sets. Securing a sufficient radial clearance between neighboring conductor segment sets will lead to reduction in the space factor of the slot.
Hence, the above arrangement makes it possible to curve or bend the tail slanting portion obliquely from the slot end surface in the radial direction. The swerved portion, formed in the vicinity of the tail joint portion, can protrude in the radial direction. Thus, it becomes possible to prevent the space factor of the slot from decreasing and also prevent the size of the stator core from increasing.
According to a preferable manufacturing method, the tail slanting portions inserted in the slots of the stator core are simultaneously tilted toward the radially outer side along the entire periphery of the stator core, so that the tail slanting portions incline to the radially outer side at the same time. According to this method, the gap between neighboring conductor segment sets disposed next to each other in the radial direction can be widened in the vicinity of the tail joint portions compared with the gap in the vicinity of an end surface of the stator core. It is needless to say that the tilt angle of the tail slanting portions toward the radially outer side is dependent on the radial position of respective tail slanting portions. The tail slanting portion positioned at the radially outer side has a larger tilt angle.
According to the stator coil of the present invention, it is also preferable that a plurality of conductor segment sets are disposed in the radial direction. Each conductor segment set is constituted by the small-turning conductor segment and the large-turning conductor segment. The small-turning conductor segment includes a small-turning head portion continuously formed with a pair of the in-slot conductor portions accommodated separately into a pair of conductor accommodation positions disposed next to each other in the radial direction. The large-turning conductor segment includes a large turning head portion straddling in the radial direction so as to surround the small-turning head portion. A group of conductor segment sets is located at the same radial position and disposed in the circumferential direction to constitute a partial phase coil to which a predetermined phase voltage is applied. And, the phase coil is constituted by serially connecting a plurality of partial phase coils having different radial positions and disposed sequentially in the radial direction.
Conventionally, the electric rotary machine using the serial-joint segmental stator coil is used for an automotive alternator. Meanwhile, it is expected that this kind of electric rotary machine is used for an automotive drive motor requiring a large output. To reduce the resistance loss caused in the stator coil and its wiring, it is necessary to supply an extremely high battery voltage (several hundreds V) to the drive motor. However, there is no substantial difference in the rotation between the segmental serial-joint type stator coil for a drive motor and the serial-joint segmental stator coil for an automotive alternator. Hence, the turn number of the serial-joint segmental stator coil for the drive motor must be increased so greatly.
Increasing the turn number of the serial-joint segmental stator coil will result in the increase in the wiring resistance. As shown in FIG. 14, the conductor segments 33a to 33e are laminated so as to form surrounded multiple layers of the conductor segments (e.g., 5 layers according to the example shown in FIG. 14). When the turn number of the serial-joint segmental stator coil is increased, the number of the in-slot conductor segments disposed in the radial direction in the slot S is increased. According to this kind of multilayered surrounded conductor segments type, many kinds of rounded conductor segments for the coil end are required by the same number as that of the laminated layers. As the outermost rounded conductor segment 33e becomes long, the overall wiring resistance increases.
Especially, due to manufacturing reasons, the rounded distal end portion H of the U-shaped conductor segment tends to have a radial width larger than that of its proximal end portion L. Although not illustrated in FIG. 14, the actual radial width W of a head side coil end 311 becomes large. The axial length of the head side coil end 311 also becomes large. The axial length of the motor is increased. The volume and weight of the motor is increased.
Furthermore, as described above, the radial width of the distal end portion H of the U-shaped conductor segment becomes larger than that of the proximal end portion L. To prevent the conductor segments from colliding with each other when they are expanded, it is necessary to secure sufficient clearance d between adjacent conductor segments disposed closely to the proximal end side of the coil end. The space factor of the slot will decrease in accordance with the increase of the clearance d.
Furthermore, the above-described surrounded multilayered structure of the conductor segments worsens the heat radiation properties of the innermost conductor segment 33a. 
To solve the above-described problems, according to this arrangement, as shown in FIG. 3, there are provided a plurality of conductor segment sets disposed in the radial direction, each of which occupies four consecutive conductor accommodation positions aligned in the radial direction in the slot. A predetermined number of conductor segment sets disposed in the circumferential direction are serially connected to constitute a partial phase coil. The phase coil is constituted by sequentially connecting the partial phase coils which are disposed in the radial direction and constituted by a plurality of conductor segment sets located at different radial positions.
According to this arrangement, the partial phase coils neighboring in the radial direction can be easily connected by using modified U-shaped conductor segments. Moreover, there is no substantial difference in the temperature and also in the wiring length between the conductor segment sets (i.e., partial phase coils) located at different radial positions. The current distribution does not concentrate locally. Excessive heat will not be produced locally. Increasing the turn number of the coil can be easily realized.
According to the stator coil of the present invention, it is also preferable that an inphase slot group is constituted by a plurality of slots adjacently and continuously disposed in the circumferential direction for accommodating in-slot conductor portions to which the same inphase voltage is applied. A plurality of serial phase coil circuits are accommodated in different slots of the inphase slot group, each serial phase coil circuit including serially connected partial phase coils accommodated in the same slot and disposed sequentially in the radial direction to have different radial positions. And, the phase coil is constituted by connecting the plurality of serial phase coil circuits in parallel with each other.
Conventionally, the electric rotary machine using the serial-joint segmental stator coil is used for an automotive alternator. Meanwhile, it is expected that this kind of electric rotary machine is used for an automotive drive motor requiring a large output. Generating a large output requires a large current. However, there is a limit in increasing the cross-sectional area of conductor segments for realizing the required large current. Hence, it is necessary to connect the partial phase coils in parallel with each other to increase an overall cross-sectional area of the phase coil. However such a parallel connection requires additional connecting wires and accordingly cannot be easily realized by sequentially connecting the conductor segments.
In view of the above, according to this arrangement, the phase coil is a serial phase coil circuit. There are provided a plurality of serial phase coil circuits. Each serial phase coil circuit is accommodated in different slots cooperatively constituting an inphase slot group. According to this arrangement, it is possible to eliminate the wiring resistance difference between respective serial phase coil circuits. Furthermore, it is possible to reduce the current difference between respective partial phase coils. Especially, even if there is some resistance difference between the partial phase coils located at different radial positions, the above-described capability of eliminating the resistance difference between respective serial phase coil circuits is very important.
Accordingly, this arrangement makes it possible to increase the turn number of the coil without using numerous kinds of conductor segments or without adding complicated or special connecting wires. Furthermore, it becomes possible to realize an excellent stator coil preferably used for an automotive drive motor to be operated under a high voltage.